Electric switch



June 24, 1941. g FETTER 2,246,581

ELECTRIC SWITCH Filed Aug. 3, 1940 ii 1AM Patented June 24, 1941 ELECTRIC SWITCH Norman C. Fetter, Freeport, Ill., assignor to Micro Switch Corporation, Freeport, 1ll., a corporation of Illinois Application August 3, 1940, Serial No. 350,603

Claims.

The present invention relates generally to electric switches, and more particularly to snap acting thermostatic electric switches.

Objects of the invention include the provision of a new and improved switch and thermostat construction, and an improved and simplified snap switch. The invention resides in certain novel feature of construction, combinations of parts, and arrangements of apparatus, and is illustrated by the specific embodiments herein shown and described by way of example. In the drawing:

Fig. 1 is a perspective view of a thermostat embodying my present invention;

Figs. 2 and 3 are partially exploded views of the device of Fig. 1, illustrating, in perspective, the various parts and their orientation with respect to each other in the assembly;

Fig. 4 is a side elevation of the device of Fig. 1;

Fig. 5 is a side elevation of a slightly modified device, and

Fig. 6 is a section taken along the line 66 of Fig. 5.

y In Figs. 1 to i inclusive, an elongated insulating base it has a central bed portion l4 and two raised or block portions 16 and it at the ends thereof. An insulating block or clamp 20 fits over the raised portion "5 and an insulating strip or guard 22 lies on the block 29 and the raised portion 18 of the base it, so as to be spaced above the central bed portion l4. Screws 24 and 26 extend down through these parts and fit into threaded bushings 28 and 30 embedded in the raised portions l6 and i8 of the base, to clamp the whole assembly together.

The raised portion l6 does not extend the full width of the base, but rather lets the bed portion l4 extend along its two sides so as to provide a s epped construction across the end of the base M. A raised lip 32 of the insulating material of the base rims the screw hole. as shown in Fi 3. A spacer 42 lies on top the raised portion l6 encircling the lip portion 32.

A U-shaped spring anchor 34, having leg por- 'rions 36, is supported on the bed portion l4 of the base. A pair of downwardly extending half punches or bl nd rivets 38 in the legs 36 fit into recesses 60 in the bed portion 84 under the block 20. The bottom face of the block or clamp 2G is recessed to conform to the stepped shape of the bed portion l4 and raised portion l6 so as to clamp the spring anchor 36 and spacer 42 tightly, to receive the projecting lip 32, and to take its alignment from the side faces of the raised part IS. The top face of the block 20 has another recess 44 for receiving a terminal plate 46, and has also an insulating lip encircling the central screw hole and extending up through the terminal plate l4 to insulate it from the binding screw 24. This lip 48 extends up above the other surfaces of the block 20 into the perforation in the top insulating strip 22.

The raised or block portion 18 at the other end of the base l2 has a central recess or depression for aligning a bimetal strip 54 and also a raised lip portion 52 surrounding the screw hole for holding the bimetal strip 54 in place and insulating it from the screw 26. The bimetal strip 54 and a U shaped spring 5658 together constitute a snap acting toggle 60. This U shaped spring includes the thin leaf compression springs 58 and the end part 58 which is riveted to the bimetal strip 54 by the contact 62. The compression springs 58 are held bowed and are supported by the spring anchor 34. A metal terminal 64 lies over the mounted end of the bimetal strip 54, and also is located and aligned by the recess 50 and both pieces are firmly clamped under insulating strip 22. The lip 52 extends up into the insulating strip or guard 22 so as to insulate the binding screw 26 from the bimetal 54 and terminal 64.

The toggle thus has its tension member supported atop the raised part l8 of the base and its two compression springs at the right end of the spring anchor 34. The end 58 at which they are connected is movable up and down to carry movable contact 62 into and out of engagement with a stationary contact 36 carried by terminal 46.

The spring anchor 34 being clamped only at one end is sufiiciently resilient to permit the other end to be flexed. A screw 68 threaded up through the bed portion [4 of the base forces the end of theanchor up to raise the axis of the mounting pivot of the compression springs 56 for adjusting the action of the snap acting toggle. Another screw 10 in the base l4 serves as a lower stop for the movable end 58 of the toggle 60.

The toggle 60 snaps up and down in response to temperature changes, opening and closing the circuit between the two contacts 62 and 66. With the bimetal mounted with its high expansion side up. the toggle snaps down in response to the temperature rise and up in response to a temperature fall. With the bimetal so arranged, raising the spring anchor 34 by means of a screw 68 lowers both the snap on and snap off temperatures without substantially changing the difierence between those two temperatures. Lowering the screw ll] will lower the snap-on temperature so as to widen the difference between the two operating temperatures of the thermostat.

Figs. 5 and 6 illustrate a modification wherein the thermostat include double throw contacts. A second metal terminal 12 similar to the terminal 46, and carrying a contact l4, replaces the spacer 42 of the construction of Figs. 1 to 4 inclusive. The screw 10 which serves as the toggle g M area-oer stop in the other construction is omitted. The

toggle carries a double faced contact 16 for separately engaging the two stationary contacts 68 and 12.

As is clearly shown in the sectional view of Fig. 6, the step of the raised portion l8 above the bed portion Id of the base, together with the recesses m the insulating clamp 20, serves to effect a firm support for the separate electrical parts 35, 6d,

and I2, and yet adequately insulates them from each other and holds them in perfect alignment,

overhang thesidesthereof and to be held in alignment thereby, an insulating cap placed over the higher'of said raised portions of said base and over said clamping block bridging the space between them, a metal fastening at either end of the resulting assembly for holding it together, a part of each metal fastening being imbedded in one of said raised portions at the ends of the base, said insulating parts having recesses under the ends of said insulating cap for receiving metal switch parts, and an electric snap switch mechanism comprising spring members and cooperating electric contacts positioned in the opening between said insulating parts, and having its parts clamped in saidrecesses under said insulating cap and between said insulating clamping block and said base.

2. In combination in an article of the class described, an elongated rectangular insulating base having a central substantially flat portion, having a raised portion of less width than said base at one end for providing steps across the width of the base, and having a second raised portion at the other end of said base, an elongated metal, spring support lying on the fiat portion of said insulating base and fitting against said first raised portion, an insulating block stepped to fit said steps extending laterally across the first end of said base and clamping one end of said spring support, said insulating block being recessed on top for supporting a stationary contact and terminal, said second raised part of said base having a recess on top, a snap acting toggle spring comprising tension and compression members having its tension member supported on the unclamped end of said spring support, the movable portion of said snap acting spring lying adjacent to the stationary contact supported from said recessed insulating block, and a contact carried by said movable portion for cooperation-with said stationary contact.

3. In combination in an article of the class described, an elongated rectangular insulating base having a central substantially flat portion, having a raised portion of less width than that of said fiat portion at one end thereof leaving extensions of said fiat mrtion of the base on second raised portion at the other end of said block. an elongated U shaped spring "support lying on the said flat portion of said insulating block and having the legs of the U lying on either side of said raised portion of the first endv of said block, an insulating clamp stepped to fit over said first raised portion, taking. its alignment therefrom, and clamping the ends of the legs of said U shaped spring support, said insulating clamping block being recessed on its top for supporting and aligning a stationary terminal, a

terminal supported therein and aligned thereby,

a contact carried by said terminal, said second raised part of said base having a recess on its top, a snap acting toggle comprising a U shaped compression spring pivoted on said spring support and a thin leaf tension spring supported and aligned in said recess on top of said second raised part of said base, the movable end of said toggle lying below said stationary contact, a contact on said movable end for cooperating V with said stationary contact, an insulating cap fitting over said second raised portion and said clamping block, and clamping the parts in place in the recesses thereof, and adjusting screws threaded through the central portion of said base for lifting the unclamped end of said spring support and for limiting the downward snap motion of the movable end of said toggle.

d. In combination in an article of the class described, an elongated rectangular insulating base having a central substantiallyfiat portion, having a raised portion at one end of said base of less width than the base for providing steps across the width of the base, and having a second raised portion at the other end of said base, an elongated, metal, toggle-spring support lying on said flat portion of said insulating base and having one end fitting alongside said first raised portion, a stationary contact and terminal lying atop said first raised portion, an insulating clamping block stepped to fit said steps extending laterally across the first end of said base as afore= said, and clamping said one end of said spring support and said stationary terminal at the different stepped levels for electrically insulating I recessed top of said second raised portion and having a compression member supported on the unclamped end of said spring support, the movable portion of said toggle spring lying between said stationary contacts and carrying electric contacts for cooperation therewith.

5. The combination of claim 1 wherein said metal fastenings pass through certain of the re= cesses between the insulating parts, and wherein said insulating parts include bushing-like extensions surrounding the' metal fastenings and passing through the clamped switch parts for insulating said switch parts from said metal fastenings while permitting said bushing-like extensions to support said switch parts against lateral displacement.

NORMAN c. FETTER. 

